CI 77491, known as iron oxide red, is chemically classified as an inorganic colorant. This pigment is composed primarily of ferric oxide (Fe₂O₃) and is widely used in various industrial and cosmetic applications 

CI 77491 is an insoluble powder but miscible in oils and water. It has high covering power and high tinting strength. It is easily dispersible, shows excellent light fastness and resistance to external weathering. 

Chemical Composition and Structure

CI 77491 is an inorganic compound with the chemical formula Fe₂O₃. It consists chiefly of ferric oxide, which is iron in the +3 oxidation state combined with oxygen. This composition gives the pigment its characteristic red color.

Physical Properties

This pigment typically appears as a fine red powder. It has a high density and excellent covering power. CI 77491 is known for its chemical stability, resistance to light and heat, and inert nature, making it suitable for long-lasting applications. Its opacity and strong tinting strength make it a versatile pigment for various uses.

Industrial Production Process

• Preparation of reagents. The main raw materials include iron compounds such as ferrous sulfate (FeSO₄) and an oxidizing agent like oxygen or hydrogen peroxide.
• Synthesis of ferric oxide. The production of CI 77491 begins with the oxidation of ferrous sulfate in the presence of an oxidizing agent. This process converts iron (II) to iron (III), forming ferric oxide (Fe₂O₃).
• Filtration. The resulting suspension is filtered to separate the solid ferric oxide from the aqueous solution.
• Washing. The ferric oxide is washed with deionized water to remove any soluble impurities.
• Drying. The washed ferric oxide is dried at controlled temperatures to remove residual moisture and obtain a dry powder.
• Grinding. The dried ferric oxide is ground to obtain a fine and uniform powder. This step may involve the use of ball mills or other grinding machinery.
• Classification. The dried powder is classified to ensure a uniform particle size. This step may involve sieving or the use of air classifiers.
• Stabilization. The CI 77491 powder is stabilized to ensure its stability during transportation and storage, preventing oxidation and aggregation.
• Quality control. The CI 77491 undergoes rigorous quality testing to ensure it meets standards for purity, color intensity, and safety. These tests include chemical analysis, spectroscopy, and physical tests to determine particle size and rheological properties.

Iron oxide and hydroxide are chemicals of various colors used as food additives in the food industry and are labeled with the number E172 as food additives and as CI 77491 as colorants.

The complete table includes:

• E172 (i) black iron oxide, CI 77499
• E172 (ii) red iron oxide, CI 77491
• E172 (iii) yellow iron oxide, CI 77492

Typical characteristics of commercial dyes:

Industrial surface treatments:

• With Triethoxycapilisilane, are easily dispersible in oil, has optimal hydrophobicity.
• With Lauroyl Lysine has optimal skin affinity, is hydrophobic and will look smooth and soft.
• With Perfluorooctyl Triethoxysilane is suitable for long lasting makeup products, excellent hydrophobicity and oleophobicity.
• With Titanium dioxide you can create different shades of color.

What it is used for and where

Cosmetics, construction, paints, detergents, waterproof flooring, ceramics, PVC, plastics, glues, pharmaceuticals, medicine.

Cosmetics - INCI Functions

• Colorant. This ingredient has the function of colouring the solution in which it is inserted in a temporary, semi-permanent or permanent manner, either alone or in the presence of the complementary components added for colouring.

Restricted cosmetic ingredient as IV/135  a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Substance or ingredient reported:

• Iron Oxide red. Wording of conditions of use and warnings:  Purity criteria as set out in Commission Directive 95/45/EC (E172)

CI 77491 is used in cosmetic products such as blushes, eyeshadows, lipsticks, and foundations due to its rich red color and high opacity. 

Industrial Applications

Paints and Coatings: In the paint industry, iron oxide red is used to achieve deep red shades and enhance UV resistance. Its stability and strong tinting properties make it ideal for both decorative and protective coatings.

Plastics and Polymers: This pigment is employed in the production of plastics and polymers to improve color uniformity and opacity. It is commonly used in products like automotive parts, packaging materials, and consumer goods.

Ceramics and Glass: CI 77491 is used in the production of ceramics and glass to achieve stable red colors. It is particularly valued for its resistance to high-temperature processes.

Inks: The pigment is also used in printing inks to produce intense red colors, ensuring high-quality and durable prints.

Safety

CI 77491 is generally considered safe for use in consumer products when handled according to proper safety procedures. It is important to avoid inhalation of the powder and minimize direct contact with skin and eyes (1). 

Studies

Ultraviolet rays from the sun cause skin aging and smartphones emit high-energy visible light from which you should protect yourself. Iron oxides (yellow, red and black) in sunscreens have the property of effectively blocking high-energy visible light especially when combined with zinc oxide (2).

The Panel on Food Additives and Nutrient Sources added to Food provides a scientific opinion re‐evaluating the safety of iron oxides and hydroxides used as food additives (E 172): yellow iron oxide (FeO(OH)·H2O), red iron oxide (Fe2O3) and black iron oxide (FeO·Fe2O3). Brown Iron Oxide has been included in this assessment for completeness, due to its importance as a commercial blend. The Panel considered that the particle size and particle size distribution should be included in the specifications. In 1980, an ADI of 0‐0.5 mg/kg bw/day was established by JECFA. Absorption of iron from iron oxides is low. The acute oral toxicity of iron oxides is greater than 10 g iron oxide/kg bw. From a subacute and a subchronic toxicity study, the Panel identified a NOAEL for red iron oxide of 1 000 mg/kg bw/day, the highest dose tested. Red (Fe2O3) and black (FeO·Fe2O3) iron oxide, both in nano‐ and micro‐form, were positive in in vitro genotoxicity assays in mammalian cells. Due to the limitations of the database, and considering the impossibility to read‐across between iron oxides with different redox state, the Panel considered that the genotoxicity of iron oxides cannot be evaluated based on the available data. Concerning carcinogenicity and reproductive and developmental toxicity, no signs of toxicity were observed in unpublished studies which were not available and could not be evaluated by the Panel. The Panel concluded that an adequate assessment of the safety of E 172 could not be carried out because a sufficient biological and toxicological database was not available. Refined exposure estimates show that exposure to E 172 ranged from 0.03 mg/kg bw/day for infants to 3.7 mg/kg bw/day for toddlers at the mean and from 0.1 mg/kg bw/day for infants to 9.5 mg/kg bw/day for toddlers at the 95th percentile for the non‐brand‐loyal scenario (3).

Red iron oxide CI 77491 studies

Molecular Formula : Fe₂O₃

Molecular Weight : 159,69

CAS : 1332-37-2

EC number   215-722-3   215-168-2   257-870-1

UNII   1K09F3G675

Synonyms:

Ferric Oxide Red

Pigment Brown 6

Pigment Brown 7

References_______________________________________________________________________

(1) Aquilina, G., Azimonti, G., Bampidis, V., de Lourdes Bastos, M., Bories, G., Chesson, A., ... & Wester, P. (2016). Safety and efficacy of iron compounds (E1) as feed additives for all species: ferric oxide based on a dossier submitted by Poortershaven Industriële Mineralen BV. EFSA JOURNAL, 14(6), 1-26.

Abstract. The additive under assessment, ferric oxide, contains between 57% and 69% iron (Fe). The EFSA FEEDAP Panel could not conclude on the safety of ferric oxide for the target animals owing to that (i) the application of ferric oxide red is for all animal species, (ii) lifetime administration to animals is not excluded and (iii) a sufficient biological and toxicological database was not available. Regarding (i) the very low absorption of iron from the ferric oxide by target animals and (ii) the homoeostatic regulation of iron metabolism in animals, any influence of feeding the ferric oxide on the iron content of edible tissues and products is not expected. The use of ferric oxide in animal nutrition is unlikely to result in a direct exposure of the consumer to this oxide. Consequently, the supplementation of feed for food-producing animals with ferric oxide would likely not constitute a risk to consumers. Ferric oxide is an irritant to skin and eyes by mechanical action. Owing to the nickel content in the additive, the ferric oxide

(2) Bernstein EF, Sarkas HW, Boland P. Iron oxides in novel skin care formulations attenuate blue light for enhanced protection against skin damage. J Cosmet Dermatol. 2021 Feb;20(2):532-537. doi: 10.1111/jocd.13803. 

(3) EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS)
First published: 08 December 2015 https://doi.org/10.2903/j.efsa.2015.4317